Mandrel apparatus for tube bending



Nov. 3, 1964 c. F. HAUTAU 3,155,139

MANDREL APPARATUS FOR TUBE BENDING Filed Sept. 25, 1961 2 Sheets-Sheet 1 INVENTOR. C/IAWPlES F. #40140.

Nov. 3, 1964 c. F. HAUTAU 3,155,139

MANDREL APPARATUS FOR TUBE BENDING Filed Sept. 25, 1961 2 Sheets-Sheet 2 j a 3/ 33 3/ 33 .31 3 3; xi a 1: 2

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G'l/JAAA'S F. #40740 d hw/dw United States Patent 3,155,139 MANBREL APPARATUS FOR TUBE BENDENG Charles F. Hautau, Oxford, Uhio, assignor to Baldwin- Lima-l-lamilton Corporation, Philadelphia, Pa, a corporation of Pennsylvania Filed Sept. 25, 1%1, sr. No. 14%,445 7 Claims. (Cl. 153-19) This invention relates to apparatus for feeding a man drel into a machine for bending tubing.

One technique for bending tubing consists of clamping a linear portion of the tubing in a stationary position and either wiping the tubing about a form or clamping the tubing against the form and rotating the clamp and form about the axis of the form. Due to the tendency of the metal on the inside face of the bend to wrinkle or buckle and since such wrinkling depends on the ratio between pipe radius and wall thickness, the conventional method is limited as to the size and type of tubing which may :be successfully bent. One method of preventing such wrinkling is to insert some type of support such as a mandrel within the interior of the tube. This mandrel may either take the form of a snake which assumes the shape of the pipe as it is bent, or a shoe which is disposed at the beginning of the bend and supports the wall of the pipe through the first few degrees of the bend, the portion in which col-lapse of the tube normally occurs. In accordance with prior practice, these snakes or shoes were placed on the end of long rods for insertion into the tubing. The rod was necessarily as long as the longest piece of tubing to be handled by the bending machine.

This invention contemplates a mandrel disposed on the end of a length of flexible cable having a radius smaller than that of the smallest pipe which can be accommodated in the machine. The cable is stored in a tube disposed parallel and adjacent to the supporting structure of the bending machine. The cable is passed into the storage tube through a 180 degree bend so that the storage tube may be placed under the machine proper. An alternative method contemplates winding the cable about a winch.

In either event, the forward end of the cable which carries the mandrel is normally disposed at a point on the axis of the tube beyond the extension of the longest workpiece which can be accommodated in the machine. The cable is moved by a pair of powered rubber wheels, which engage the cable on opposite sides. Alternately, if a winch is used as a storage means, the cable could be powered by rotating the winch. A series of movable blocks support the cable at spaced points along the cable as it moves in and out of the tubing.

It is therefore an object of the present invention to provide means, in a tube bending machine, for feeding a mandrel into the interior of the tubing, positioning the mandrel at the point where bending begins, and for retracting the mandrel after the bending operation.

It is another object of this invention to provide a flexible rod or extension for the mandrel, and suitable means for storing the rod while the tubing is placed in the bending machine.

A further object of the present invention is to provide support means for the mandrel and flexible rod between the end of the tubing and the storage area.

Other objects and advantages of the present invention will be made apparent by the following detailed description wherein is disclosed a preferred embodiment of the present invention. The description makes reference to the accompanying drawings in which:

FIGURE 1 is a perspective view of a stretch bending machine incorporating the present invention.

3,1553% Patented Nov. 3, 1964 "ice FIGURE 2 is a detail sectional view taken through the bending forms shown in FIGURE 1.

FIGURE 3 is a detail sectional view of a mandrel and support blocks which may be employed in the present invention.

FIGURE 4 is a detail sectional view of a mandrel which may be employed in the present invention, in its retracted position.

FIGURE 5 is a detail sectional view of the mandrel of FIGURE 4.

FIGURE 6 is a detail sectional view of a second mandrel which may be employed in the present invention.

With reference to the drawings, FIGURE 1 shows an automatic tube stretch-bending machine incorporating a preferred embodiment of the present invention. The machine is illustrated with the hydraulic and electronic systems removed for simplicity. These systems may be of a class well known to those skilled in the art and a particular variety is described in greater detail in my copending application Serial No. 16,846, filed March 22, 1960.

The machine is supported on a base 10 which may be welded plate construction. To the left of the machine, as shown in FIGURE 1, a pipe support stand 12 which is supported on two legs 14 is adapted to support the pipe 16 as it enters the machine. A mandrel snake 18 or shoe 2% is attached to the end of a flexible cable 22 which may be constructed of small steel wires or of any suitable material such as will allow the cable 22 to take compressive forces over short lengths when it is stored, but will also be sufliciently flexible so as to allow the cable to easily conform to a large radius. The cable is stored in a storage tube 24 disposed parallel to the supporting structure of the machine. A pair of wheels 26, of suitable material so as to engage the cable 22, is powered by a hydraulic motor at 28.

The cable 22 is of such length that in its retracted position, the mandrel snake 18 or shoe 20 will be situated just short of the free end of the longest workpiece which the machine can accommodate. If the workpiece is of less than this maximum length, the mandrel 18, 2t? and its adjacent cable 22 will be required to move through some distance to reach the end of the pipe 16. To provide support for the cable 22 as it moves through this distance, and to guide it'toward the interior of the pipe 16, a series of movable blocks 30 are threaded along the cable 22 behind the mandrel 18 and move in a channel 32 disposed parallel to the extension of the tubing 16 and slightly below it. The guide blocks 30 are fitted with T emensions 31 of various widths which are accommodated by stops 33 extending perpendicularly from the flanges of the channel 32. When the cable 22 is initially energized to move the mandrel 18 toward the free end of the tubing 16, the guide blocks 30 are moved forward due to the attraction of magnets 35 sunk in the surfaces of the blocks 30 and the mandrel 18, 20, as shown in FIGURE 4, and station themselves at regular intervals along the otherwise unsupported length of the cable 22 between the wheels 26 and the tube to be bent. As the cable 22 is retracted from the interior of the tubing 16, the guide blocks 30 are pulled back along the channel 32 by the mandrel 18, 20 which has a diameter greater than that of the openings in the guide blocks Stl. An alternative method of spacing the blocks 3i) consists of utilizing a .series of detent attachments between the guide blocks 30 and the cable 22.

The wheels 26 and the motor 28 are arranged so as to propel the mandrel 18 through the tubing to its normal station during the bending process. If a snake type mandrel 18 (FIGURE 6) is employed, the snake 18 would have to project from the free end of the tube.

If a shoe type mandrel 26 (FIGURE 5 is employed, the shoe 2% would be disposed with its end projecting just eyond the point at which bending begins.

A chuck 34, slidably mounted on slide rods 36, is positioned along the slide rods 36 by'a hydraulic motor 38. The chuck 34 has jaws 4b which may be opened or closed by a hydraulic cylinder 42 or revolved by a hydraulic motor 44 by means of gears (not shown) in a manner well known to the art. A stationary clamp 46, operated by a hydraulic cylinder 48 locks the pipe in place during the bending operation.

The bending apparatus consists of a column of annular bending forms 50 of varying diameter mounted on a screw 52, and an arm 54 fixed so as to rotatably move about the screw 52. As shown in FIGURE 2, each of the forms 5t) permit a dilierent radius of bend. A hydraulic motor 56 engages a gear (not shown) which is mounted on the screw 52 so that rotation of the motor 56 revolves the screw 52 and enables the desired bending form 50 to be moved vertically into position adjacent the pipe 16. A bending clamp 58, operated by a hydraulic cylinder 6t), locks the workpiece firmly between the clamp 53 and the form Stl. A hydraulic motor 62 rotates a pinion 64 which engages a gear 66 permanently affixed to both the forms 5%) and the arm 54 in such a manner as to rotate the forms 50 and the arm 54. at the same rate. The screw 52 is located in a housing 68 which is permanently affixed to a slide block 7%, slidably mounted in longitudinal ways '72. The entire assembly of forms 5% arm 5d, slide block 70"and longitudinal ways 72, is slidably mounted in lateral ways 74 and may be moved in the lateral ways 74 by a hydraulic motor '76. The movement of the slide block along the longitudinal ways 72 is limited by a passive hydraulic cylinder '78 which is preset to prevent movement of the slide block 70 until the stress in the pipe 16 reaches a value in excess of the yield strength, but less than the ultimate strength, of the pipe material.

In operation, the arm 54 is swung to its open position perpendicular to the axis of the pipe 16, with the bending clamp 58 in an open position. The bending forms 59 are raised or lowered until the form having the desired radius of bend is at the same elevation as the pipe 16. The entire assembly of forms 59, arm 54, slide block 7% and longitudinal ways 72 is moved laterally until the bending form St? is immediately adjacent to the pipe E6. The cable 22 and snake 18 or shoe 29 are retracted (to the left in FIGURE 1) and the stationary clamp 46 opened so as to allow the pipe 16 to be placed in the chuck 34. The hydraulic cylinder -52 and motors 38, 44 are activated, positioning the desired point on the pipe 16 between the bending clamp 58 and the forms 50. The stationary clamp 6 is closed and the cable 22 moved forward (to the right in FIGURE 1) until the snake 18 or shoe 2% is disposed at the point of bending. The bending clamp 58 is closed, locking the pipe 16 between the clamp 58 and the form 50. The hydraulic motor n2 is activated, rotating the arm 54 and forms 5%, pulling the pipe 16 around the form 56.

Due to the resistance in the pipe length between the stationary clamp 46 and the forms 55), there is a tendency for the arm 54 and forms 59 to move or wal towards the stationary clamp 46 as the pipe 16 is pulled around the forms 5%. The hydraulic cylinder '78 resists such movement with the result that the pipe 16 is stretched between the bending clamp 58 and the stationary clamp 56. When the stress on the pipe 16, and hence the force on the slide block 7%, reaches a predetermined value in excess of the yield stress but less than the ultimate strength of the pipe material, the resistance of the cylinder 78 is overcome and the arm 54, forms 5%, and slide block 70 move towards the stationary clamp 46. The pipe 16 is thus simultaneously bent and stretched past its yield limit but below its ultimate limit.

After the arm 54 and forms 5t? have rotated through v forced out of the hydraulic cylinder '78.

d the desired arc distance, the bending clamp 58 is opened and the chuck assembly 34, ill actuated to rotate the pipe 16 and move it forward (to the right in FIGURE 1) along its axis to its new desired position adjacent the forms St The bending operation is then repeated.

if the shoe mandrel 20 (FIGURE 5) is utilized, means must be provided to retract the mandrel 2d at the same rate that the forms 56 and the arm 54 walk back towards the clamp This may be accomplished by connecting the hydraulic motor 28 to the fluid relief valve in the hydraulic cylinder 2% in such manner that the wheels 26 will retract the cable 22 and mandrel 20 when fluid is If the snake mandrel it (FiGURE 6) is employed, such retracting means are not necessary since the snake is may be bent with the pipe 16 around the form 50.

Although the above embodiment illustrates the present invention incorporated in an automatic stretch bending machine, the invention may also be successfully employed in machines of the non-automatic variety and in machines which employ ditferent bending techniques.

This invention may be embodied in other forms or carried out in other ways without departing from the spirit or essential characteristics thereof. The present embodiment of the invention is therefore to be considered as in all respects illustrative and not restrictive, the scope of the invention being indicated by the appended claims, and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein.

Having thus described my invention, I claim:

1. in a machine for bending tubing having means for maintaining a portion of said tubing in a stationary position during bending, the improvement for feeding a mandrel into the interior of said tubing to support the interior walls of said tubing at the point of bending, comprising: a flexible elongated member disposed and movable along the axis of said portion of said tubing, said member having an outer diameter smaller than the inside diameter or" said tubing; a mandrel fixed at one end of said member; power means for retracting said member to a position exterior of said tubing, and for extending said member to a point along the interior of said tubing where bending is to begin; and means receiving the other end of said member for storing said member alongside of the axis of said portion of said tubing.

2. in a machine for bending tubing having means for maintaining a portion of said tubing in a stationary position during bending, the improvement for feeding a mandrel into the interior of said tubing to support the interior walls of said tubing at the point of bending, comprising: a flexible elongated member disposed and movable along the axis of said portion of said tubing, said member having an outer diameter smaller than the inside diameter of said tubing; a mandrel fixed at one end of said member; power means for retracting said member to a first point exterior of said tubing, and for extending said member to a second point in the interior of said tubing where bending is to begin; track means for guiding said member between said first and said second positions; and a storage tube disposed parallel to and displaced from the axis of said portion of said tubing, said storage tube being adapted to maintain that portion of said member which extends beyond said track means on the opposite side of said track means from said tubing, in return relation with respect to the remaining portion of said member.

3. In a machine for bending tubing having means for maintaining a portion of said tubing in a stationary position during bending, the improvement for feeding a mandrel into the interior of said tubing to support the interior walls of said tubing at the point of bending, comprising: a flexible elongated member disposed and movable along the axis of said portion of said tubing, said member having an outer diameter smaller than the inside diameter of said tubing; a mandrel fixed at one end of said member; power means for retracting said member to a first point exterior of said tubing and for extending said member to a second point along the interior of said tubing, where bending is to begin; a series of supports slidably disposed along said member behind said mandrel; means for spacing said supports between said first point and the end of said tubing proximate to said first point as said member is moved towards said end of said tubing; means for retracting said supports'towards said first point as said mandrel is retracted from said end of said tubing; and means for storing said member exteriorly of the axis of said portion of said tubing.

4. In a machine for bending tubing having means for maintaining a portion of said tubing in a stationary posi tion during bending, the improvement for feeding a mandrel into the interior of said tubing to support the interior walls of said tubing at the point of bending, comprising; a flexible elongated member disposed and movable along the axis of said portion of said tubing, said member having an outer diameter smaller than the inside diameter of said tubing; a mandrel fixed at one end of said member; power means for retracting said member to a first point exterior of said tubing and for extending said member to a second point along the interior of said tubing, where bending is to begin; a stationary channel disposed parallel to the axis of said portion of said tubing; a series of stops of various lengths disposed along the inside face of each flange of said channel and extending penpendicularly to said flanges; a series of blocks threaded along said member and movable in said channel, said blocks having T-extensions of various widths each of which is accommodated by one of said stops in said channel, such that said blocks are spaced along said channel between said first point and the end of said tubing proximate to said first point as said member is moved towards the end of said tubing; and storing means for said member displaced from the axis of said portion of said tubing.

5. In a machine for bending tubing wherein said tubing is initially placed in position along a first axis and subsequently bent into a desired configuration, the improvement for feeding a mandrel into the interior of said tubing to support the interior walls of said tubing at the point of bending, comprising; a flexible elongated member disposed and movable along said first axis, said member having an outer diameter smaller than the inside diameter of said tubing; a mandrel fixed at one end of said member; power means for retracting said member along said first axis to a position exterior of said tubing, and for extending said member along said axis to a point along the interior of said tubing where bending is to begin; and storing means for storing at least a major portion of said member when said member is not in use and for causing at least a portion of said member to bend into a storage position wherein at least a major portion of said member is ofiset with respect to said axis.

6. In a machine for bending tubing wherein said tubing is initially placed in position along a first axis and subsequently bent into a desired configuration, the improvement for feeding a mandrel into the interior of said tubing to support the interior walls of said tubing at the point of bending, comprising: a flexible elongated member disposed and movable along said first axis, said member having an outer diameter smaller than the inside diameter of said tubing; a mandrel fixed at one end of said member; power means for retracting said member along said first axis to a position exterior of said tubing, and for extending said member along said axis to a point along the interior of said tubing where bending is to begin; and a storage receptacle displaced from said axis, said receptacle being adapted to maintain a portion of said member at the end thereof opposite to said mandrel in bent position with respect to the remaining portion of said member.

7. In a machine for bending tubing wherein said tubing is initially placed in position along a first axis and subsequently bent into a desired configuration, the improvement for feeding a mandrel into the interior of said tubing to support the interior walls of said tubing at the point of bending, comprising: a flexible elongated member disposed and movable along said first axis, said member having an outer diameter smaller than the inside diameter of said tubing; a mandrel fixed at one end of said member; power means for retracting said member along said first axis to a position exterior of said tubing, and for extending said member along said axis to a point along the interior of said tubing where bending is to begin; and a storage receptacle disposed parallel to and displaced from said axis, said receptacle being adapted to maintain a portion of said member at the end thereof opposite to said mandrel in return relation with respect to the remaining portion of said member.

References Cited in the file of this patent UNITED STATES PATENTS 2,119,875 Carl June 7, 1938 2,306,223 Parker et a1 Dec. 22, 1942 2,382,745 Powers Aug. 14, 1945 2,777,500 Ekholm et al. Jan. 15, 1957 

1. IN A MACHINE FOR BENDING TUBING HAVING MEANS FOR MAINTAINING A PORTION OF SAID TUBING IN A STATIONARY POSITION DURING BENDING, THE IMPROVEMENT FOR FEEDING A MANDREL INTO THE INTERIOR OF SAID TUBING TO SUPPORT THE INTERIOR WALLS OF SAID TUBING AT THE POINT OF BENDING, COMPRISING: A FLEXIBLE ELONGATED MEMBER DISPOSED AND MOVABLE ALONG THE AXIS OF SAID PORTION OF SAID TUBING, SAID MEMBER HAVING AN OUTER DIAMETER SMALLER THAN THE INSIDE DIAMETER OF SAID TUBING; A MANDREL FIXED AT ONE END OF SAID MEMBER; POWER MEANS FOR RETRACTING SAID MEMBER TO A POSITION EXTERIOR OF SAID TUBING, AND FOR EXTENDING SAID 